1. Field of the Invention
The present invention relates to an electromagnetic relay having surface-mount terminals.
2. Description of the Related Art
In recent years, surface-mounting technology has been increasingly adopted for mounting electric/electronic components on a circuit board provided in various electric apparatuses. This is also the case for an electromagnetic relay adapted to be mounted on a circuit board.
An electromagnetic relay includes various parts such as a coil, a movable contact member mechanically driven by the coil, etc., which are generally contained and supported in a housing for protection against external contaminants and thus constitute a relay body. External terminals are provided to project from the housing for mounting the electromagnetic relay on a circuit board and, in the case of a surface-mount-type electromagnetic relay, each external terminal is bent into an L-shape with the distal end portion thereof extending parallel to the bottom surface of the housing.
In a conventional surface-mounting process, solder is previously applied to a printed circuit board having wiring lines patterned thereon, at predetermined positions on which various electric/electronic components are to be mounted, and the components are then placed on the respective positions. Thereafter, the circuit board having the components placed thereon is passed through, e.g., a heating oven, so that the components and the solder are heated, and thereby the components are soldered to the printed circuit board.
Thus, the surface-mount-type electromagnetic relay is also mounted on the printed circuit board by soldering the distal end portions of the external terminals, extending parallel to the bottom surface of the body or housing, to the printed circuit board. During a time when the printed circuit board is passed through the heating oven in the soldering process, the electromagnetic relay including mechanically operating parts and thus having relatively large dimensions tends to become unstable.
Japanese Examined Utility Model Publication (Kokoku) No. 6-24113 (JP-6-24113-Y2) describes an electromagnetic relay including surface-mount-type terminals projecting from the bottom surface of a relay body and a projection also projecting from the bottom surface, the projection having a height less than the height of each terminal. The projection is adapted to be adhered onto a printed circuit board by an adhesive prior to a soldering process, and thus acts to prevent the electromagnetic relay from being shifted during the soldering process, i.e., when the electromagnetic relay is passed through a heating oven.
In an electromagnetic relay having relatively large dimensions, when the electromagnetic relay is subjected to heat in the soldering process or when heat is generated during the operation of the electromagnetic relay, a relatively large thermal stress is likely to be produced in the external terminals soldered to the printed circuit board, due to the difference in linear thermal expansion coefficient between the printed circuit board and the housing of the electromagnetic relay.